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Chlorella sp. microalgae is a potential source of natural antioxidants and other bioactive compounds used in the food and pharmaceutical industries. Ultrasound pretreatments followed by enzymolysis are widely used to improve the functional properties of biological materials. This work aimed to investigate the effects of ultrasound pretreatments followed by bromelain hydrolysis on the proteins, phenolic content, and antioxidant activity of Chlorella sp. crude extract. The experimental design for the study involved two factors: ultrasound pretreatment time (0, 5, and 10 min) and bromelain hydrolysis time (0, 2, 4, and 6 hours). The protein was measured using Lowry assay while the total phenolic content was measured using a Folin–Ciocalteu assay. The highest protein content (7.09 ± 0.44 mg/mL) and phenolic concentrations (0.28 ± 0.01 ìg/mL) were obtained at 5 min ultrasound pretreatment and 6 hours enzymolysis. For antioxidant activity, 5 min ultrasound pretreatment followed by 4 hours of enzymolysis resulted in the highest DPPH (1,1-diphenyl-2-picrylhydrazyl radical) inhibitory activity (81.74%). Meanwhile, ultrasound pretreatment for 10 min followed by 6 hours of enzymolysis resulted in the highest ABTS (2,20 azinobis-(3-ethylbenzthiazoline-6-sulfonic acid) inhibitory activity (94.10%). This study showed that variation in ultrasound pretreatments followed by bromelain hydrolysis could be used to improve the protein content, phenolic content, and antioxidant activity of Chlorella sp. crude extract.

Kombucha is a renowned fermented drink for its diverse health benefits. This research aims to evaluate sweetened red ginger extract as an alternative substrate in making kombucha by observing the chemical properties (pH, total acid, total sugar, total polyphenol, chemical compound profile using LC-MS/MS) and the antioxidant activity. Three variables were varied, i.e., red ginger concentration (1, 5, and 10%), kombucha culture concentration (10 and 20%), and fermentation time (0, 6, and 12 days). The total sugar and pH declined during fermentation while the titratable acidity, polyphenol, and antioxidant activity increased. The kombucha prepared with 20% culture concentration resulted in a greater reduction of pH and increase of titratable acidity, total polyphenol, and antioxidant activity than the one prepared with 10% culture concentration. The red ginger kombucha prepared with 10% ginger and 20% culture in 12 days displayed the highest antioxidant activity. It revealed ten active compounds under the LC-MS/MS investigation, i.e., 3’,4’,5’,5,7,8-hexame-thoxy flavone, 6-gingerol, evodin, isosakuranetin-7-rutinoside, methyl ophiopogonanone A, narirutin, neohesperidin, ononin, sinensetin, and shogaol. This research shows that red ginger extract fermentation using kombucha culture can be an alternative technology to produce red ginger-based functional drinks with healthy organic acids, healthy polyphenols, and antioxidant activity.

Tempeh is nutritious food prepared through solid-state fermentation of cooked and dehulled soybeans with Rhizopus sp. for about 48 h. Fermentation beyond 48 h resulted in over-fermented tempeh. There may or may not have been similar research done before, especially related to its antioxidant and cytotoxicity. This study aims to determine the characteristics of fermented tempeh for up to 156 h. Samples were fermented at 0, 24, 48, 60, 72, 84, 96, 108, 120, and 156 h. Samples were dried, grounded, and extracted with acetone, followed by defatting with n‑hexane. Extracts were dissolved in organic solvents for free radical scavenging activity (FRSA) and cytotoxicity assays. The 120-h tempeh extract, at the concentration of 1,000 μg/mL, demonstrated the highest FRSA (81.31% inhibition) against 100 µM 2,2-diphenyl-1-picrylhydrazyl (DPPH) solution. Meanwhile, the 108-h tempeh extract at 1,000 μg/mL possessed the highest cytotoxicity (IC50 of 2.54 μg/mL) against MCF-7 breast cancer cell lines. Liquid Chromatography-Mass Spectrometry/Mass Spectroscopy (LC-MS/MS) analysis revealed the presence of daidzin, genistin, daidzein, and genistein in all extracts. Extracts prepared from 108 h and 120 h tempeh stood out from other extracts in the Partial Least Square (PLS) bi-plot due to their high percentage of inhibition, low response of daidzin, and high responses of the other three isoflavones. The cytotoxicity assays of the standard isoflavones showed that genistein had the lowest IC50 value at 4.82 ± 0.11 μg/mL. Standard genistein showed a low percentage of inhibition at 29.79 ± 9.10.